Apparatus and method for establishing radio bearer of mobile terminal

ABSTRACT

A method for establishing radio bearer (RB) between a mobile terminal and a network in a wireless communication system. The mobile terminal receives RB information for a specific service from one or more cells and stores the received the RB information. If the mobile terminal is moved to one or more cells and then is moved back to the specific cell, the mobile terminal establishes an RB for the specific service according to the previously stored RB information of the specific cell rather than re-receiving the RB information.

CROSS-REFERENCE TO RELATED APPLICATIONS

Pursuant to 35 U.S.C. § 119(a), this application claims the benefit ofearlier filing date and right of priority to Korean Application No.2004-0001587, filed on Jan. 9, 2004, the contents of which is herebyincorporated by reference herein in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method and apparatus for establishinga radio link between a mobile terminal and a network in a wirelesscommunication system.

2. Description of the Related Art

The universal mobile telecommunications system (UMTS) is athird-generation mobile communications system evolving from the globalsystem for mobile communications system (GSM), which is the Europeanstandard. The UMTS is aimed at providing enhanced mobile communicationsservices based on the GSM core network and wideband code-divisionmultiple-access technologies.

A related art UMTS network structure 1 is illustrated in FIG. 1. Amobile terminal 2, or user equipment (UE), is connected to a corenetwork 4 through a UMTS terrestrial radio access network (UTRAN) 6. TheUTRAN 6 configures, maintains, and manages a radio access bearer forcommunications between the UE 2 and the core network 4 to meetend-to-end quality of service requirements.

The UTRAN 6 includes a plurality of radio network subsystems (RNS) 8,each of which comprises one radio network controller (RNC) 10 for aplurality of base stations 12, or “Node Bs.” The RNC 10 connected to agiven base station 12 is the controlling RNC for allocating and managingthe common resources provided for any number of UEs 2 operating in onecell. One or more cells exist in one node B. The controlling RNC 10controls traffic load, cell congestion, and the acceptance of new radiolinks. Each Node B 12 may receive an uplink signal from a UE 2 and maytransmit downlink signals to the UE. Each Node B 12 serves as an accesspoint enabling a UE 2 to connect to the UTRAN 6, while an RNC 10 servesas an access point for connecting the corresponding Node Bs to the corenetwork 4.

Among the radio network subsystems 8 of the UTRAN 6, the serving RNC 10is the RNC managing dedicated radio resources for the provision ofservices to a specific UE 2 and is the access point to the core network4 for data transfer to the specific UE. All other RNCs 10 connected tothe UE 2 are drift RNCs, such that there is only one serving RNCconnecting the UE to the core network 4 via the UTRAN 6. The drift RNCs10 facilitate the routing of user data and allocate codes as commonresources.

The interface between the UE 2 and the UTRAN 6 is realized through aradio interface protocol established in accordance with radio accessnetwork specifications describing a physical layer (L1), a data linklayer (L2) and a network layer (L3) described in, for example 3GPPspecifications. These layers are based on the lower three layers of anopen system interconnection (OSI) model that is a well-known incommunications systems.

A related art architecture of the radio interface protocol isillustrated in FIG. 2. As shown, the radio interface protocol is dividedhorizontally into the physical layer, the data link layer, and thenetwork layer, and is divided vertically into a user plane for carryingdata traffic such as voice signals and Internet protocol packettransmissions and a control plane for carrying control information forthe maintenance and management of the interface.

The physical layer (PHY) provides information transfer service to ahigher layer and is linked via transport channels to a medium accesscontrol (MAC) layer. Data travels between the MAC layer and the physicallayer via a transport channel. Also, data transmission is performedthrough a physical channel between different physical layers, namely,between physical layers of a sending side (transmitter) and a receivingside (transmitter).

The MAC layer of the second layer (L2) provides information transferservice to a higher layer and is linked via a logical channel to a radiolink control (RLC) layer. The RLC layer of the second layer (L2)supports the transmission of reliable data and can perform segmentationand concatenation functions for RLC service data units (SDU) receivedfrom an upper layer.

The radio resource control (RRC) layer located at the lowest portion ofthe third layer (L3) is only defined in the control plane and controlstransport channels and physical channels with respect to theestablishment, re-establishment, and releasing of radio bearers. A radiobearer (RB) is a service provided by a lower layer, such as the RLClayer or the MAC layer, for transferring data between the UE 2 and theUTRAN 6.

The establishment of an RB determines regulating characteristics of theprotocol layer and channel needed to provide a specific service, therebyestablishing the parameters and operational methods of the service. Whena connection is established to allow transmission between an RRC layerof a specific UE 2 and an RRC layer of the UTRAN 6, the UE 2 is said tobe in the RRC-connected state. Without such connection, the UE 2 is inan idle state.

Hereafter, a Multimedia Broadcast/Multicast Service (MBMS or “MBMSservice”) will be described. MBMS refers to a method of providingstreaming or background services to a plurality of UEs 2 using adownlink-dedicated MBMS radio bearer that utilizes at least one ofpoint-to-multipoint and point-to-point radio bearer. One MBMS serviceincludes one or more sessions and MBMS data is transmitted to theplurality of terminals through the MBMS radio bearer only while thesession is ongoing.

As the name implies, an MBMS may be carried out in a broadcast mode or amulticast mode. The broadcast mode is for transmitting multimedia datato all UEs 2 within a broadcast area, for example the domain where thebroadcast is available. The multicast mode is for transmittingmultimedia data to a specific UE 2 group within a multicast area, forexample the domain where the multicast service is available.

The UTRAN 6 provides the MBMS service to the UEs 2 using the RB. RBsused by the UTRAN 6 can be classified as a point-to-point RB or apoint-to-multipoint RB. The point-to-point RB is a bi-directional RB,including a logical channel DTCH (Dedicated Traffic Channel), atransport channel DCH (Dedicated Channel) and a physical channel DPCH(Dedicated Physical Channel) or SCCPCH (Secondary Common ControlPhysical Channel).

The point-to-multipoint RB is a unidirectional downlink RB, including alogical channel MTCH (MBMS Traffic Channel), a transport channel FACH(Forward Access Channel), and the physical channel SCCPCH. The logicalchannel MTCH is configured for each MBMS service provided to one celland used to transmit user plane data of a specific MBMS service to theUEs 2.

The UTRAN 6 providing the MBMS service transmits MBMS-related RRCmessages to the plurality of terminals (UEs 2) through an MCCH (MBMSControl Channel). Herein, the logical channel MCCH is thepoint-to-multipoint downlink channel and is mapped to the FACH, which ismapped to the SCCPCH.

The MBMS-related RRC messages transmitted through the MCCH typicallycomprise an MBMS service information message and an MBMS RB informationmessage. The MBMS service information message transmitted to each cellincludes a list of IDs for MBMS services ongoing, or set to be ongoing,in a corresponding and the type of RB for each MBMS service. If thespecific MBMS service uses the point-to-multipoint RB in thecorresponding cell, the MBMS RB information message includes informationof the point-to-multipoint RB related to the corresponding MBMS service.

A terminal desiring to receive the specific MBMS service using thepoint-to-multipoint RB receives the MBMS service information messagethrough the MCCH. If the received MBMS service information messageindicates receiving the MBMS RB information message for the specificMBMS service, the terminal obtains information required for establishingan MBMS RB for receiving the specific MBMS in the terminal through theMBMS RB information message. In other words, if the received MBMSservice information message includes an ID of the specific MBMS serviceand indicates that a type of RB for the specific MBMS is apoint-to-multipoint RB, the terminal obtains point-to-multipoint RBinformation by receiving the MBMS RB information message and establishesthe point-to-multipoint RB by using the information.

A related art process for establishing the MBMS RB for the specific MBMSservice in a cell into which the mobile terminal (UE 2) has moved isillustrated in FIG. 3. As shown in FIG. 3, the mobile terminal movesfrom a cell A to a cell B, from the cell B to a cell C, and then fromthe cell C to the cell A. The UE 2 sequentially performs the steps 1, 2,3 and 4 in the cells A-C.

The cells A-C provide a specific MBMS service the mobile terminal (UE 2)desires to receive, and transmit the MBMS service to the mobile terminalusing a point-to-multipoint RB. Whenever the mobile terminal moves intoa new cell, it receives an MBMS service information message and an MBMSRB information message. The UE 2 then establishes thepoint-to-multipoint RB for the new cell using the received informationmessages.

In step 1, the mobile terminal is positioned in the cell A and a sessionof the specific MBMS service desired to be received by the mobileterminal starts at this time. When the session starts, the mobileterminal receives an MBMS RB information message transmitted in the cellA and obtains information for a point-to-multipoint RB. The mobileterminal then establishes a point-to-multipoint MBMS RB using theobtained point-to-multipoint RB information and receives data of thespecific MBMS service. Subsequently, the mobile terminal moves from thecell A to the cell B for performing step 2.

Thereafter, in steps 2, 3 and 4, the mobile terminal receives an MBMS RBinformation message transmitted from the corresponding cell while movingfrom one cell to other, and obtains point-to-multipoint MBMS RBinformation. The mobile terminal then establishes thepoint-to-multipoint MBMS RB using the obtained point-to-multipoint RBinformation and receives data of the specific MBMS from thecorresponding cell.

According to the related art radio bearer establishing method of amobile terminal, whenever the mobile terminal receives a specific MBMSservice through a point-to-multipoint RB while moving through severalcells, the mobile terminal will have received an MBMS RB informationmessage for establishing an MBMS RB each time the mobile terminal movesinto a cell. Accordingly, like step 4 of FIG. 3, when the mobileterminal returns to a cell previously entered into, such as the cell A,after passing through the other cells (cells B and C), the mobileterminal unnecessarily receives again the MBMS RB information message ithad previously received for establishing the MBMS RB. This operation isproblematic because the unnecessary reception of the MBMS RB informationmessage causes a time delay in receiving MBMS service data after themobile terminal moves into the cell and the MBMS RB is set. Furthermore,data is lost because the data cannot be received due to the delay.

SUMMARY OF THE INVENTION

The present invention is directed to a method for establishing a radiobearer (RB) of a mobile terminal to prevent re-receiving apoint-to-multipoint radio bearer information message and to minimizedata loss when the mobile terminal moves between cells.

Additional features and advantages of the invention will be set forth inthe description which follows, and in part will be apparent from thedescription, or may be learned by practice of the invention. Theobjectives and other advantages of the invention will be realized andattained by the structure particularly pointed out in the writtendescription and claims hereof as well as the appended drawings.

To achieve these and other advantages and in accordance with the purposeof the present invention, as embodied and broadly described, the presentinvention is embodied in a method and apparatus. In an exemplaryembodiment, a method for establishing a radio link between a mobileterminal and a network in a wireless communication system comprisesestablishing communication with the network in a cell, receiving andstoring radio bearer information associated with the cell, disconnectingcommunication with the network in the cell, reestablishing communicationwith the network in the cell, and establishing a point-to-multipointradio bearer for a service using the stored radio bearer informationupon reestablishing communication with the network in the cell.

In one aspect, the radio bearer information is received through an MBMScontrol channel (MCCH) of the cell. The method further comprisesestablishing a point-to-multipoint radio bearer for a service using theradio bearer information and receiving the service prior todisconnecting communication with the network. The service may comprise apoint-to-multipoint service. Further, the radio bearer information maybe point-to-multipoint radio bearer information.

In a detailed aspect, the method further comprises receiving a cell IDof the cell, determining a type of the received radio bearer informationassociated with the cell, establishing a point-to-point radio bearer fora service using the received radio bearer information if the receivedradio bearer information is determined to be point-to-point radio bearerinformation, and receiving the service using the point-to-point radiobearer.

In another aspect, the method further comprises receiving a cell ID ofthe cell, determining whether the cell ID and point-to-multipoint radiobearer information of the cell are stored in a memory if the receivedradio bearer information is determined to be point-to-multipoint radiobearer information, establishing a point-to-multipoint radio bearer fora service using the point-to-multipoint radio bearer information if itis determined that the cell ID and the point-to-multipoint radio bearerinformation of the cell are stored in the memory, and receiving theservice using the point-to-multipoint radio bearer.

In yet another aspect, the method further comprises receiving a cell IDof the cell, determining whether the cell ID and point-to-multipointradio bearer information of the cell are stored in a memory if thereceived radio bearer information is determined to bepoint-to-multipoint radio bearer information, storing the cell ID andthe received radio bearer information in the memory if it is determinedthat either the cell ID or the point-to-multipoint radio bearerinformation is not stored in the memory, establishing apoint-to-multipoint radio bearer for a service using the received radiobearer information, and receiving the service using thepoint-to-multipoint radio bearer.

In another aspect, the method further comprises receiving a cell ID ofthe cell, receiving update information of a point-to-multipoint radiobearer for a service, and determining whether the cell ID andpoint-to-multipoint radio bearer information of the cell are stored in amemory, wherein the update information is received through an MBMScontrol channel (MCCH) of the cell.

The method further comprises receiving current update information of apoint-to-multipoint radio bearer associated with the cell if it isdetermined that the cell ID and the point-to-multipoint radio bearerinformation are stored in the memory, comparing the current updateinformation of the point-to-multipoint radio bearer with stored updateinformation of the point-to-multipoint radio bearer, establishing apoint-to-multipoint radio bearer for the service using the stored updateinformation of the point-to-multipoint radio bearer if the currentupdate information of the point-to-multipoint radio bearer is the sameas the stored update information of the point-to-multipoint radionbearer, and receiving the service using the point-to-multipoint radiobearer.

In another aspect, the method further comprises receiving a cell ID ofthe cell, receiving update information for a service, determiningwhether the cell ID and point-to-multipoint radio bearer information ofthe cell are stored in a memory, comparing the received updateinformation with previously stored update information if it isdetermined that either the cell ID or the point-to-multipoint radiobearer information is not previously stored in the memory, and receivingcurrent point-to-multipoint radio bearer information associated with thecell if the received update information is different from the storedupdate information.

The method further comprises storing the cell ID, the currentpoint-to-multipoint radio bearer information and the received updateinformation in the memory, establishing a point-to-multipoint radiobearer for the service using the current point-to-multipoint radiobearer information, and receiving the service using thepoint-to-multipoint radio bearer.

In a further aspect, storing radio bearer information associated withthe cell comprises determining whether a number of radio bearerinformation items to be stored exceeds a threshold value in the mobileterminal, deleting a previously-stored radio bearer information item andstoring the radio bearer information if the number of radio bearerinformation items to be stored exceeds the threshold value in the mobileterminal, and storing the radio bearer information if the number ofradio bearer information items to be stored does not exceed thethreshold value in the mobile terminal. The threshold value in themobile terminal may be determined by the network or by the mobileterminal.

In one aspect, deleting a previously-stored radio bearer informationitem comprises deleting the radio bearer information item of a cellpositioned farthest from the cell the mobile terminal is currently in.Furthermore, deleting a previously-stored radio bearer information itemcomprises deleting the oldest radio bearer information item among thestored radio bearer information items.

In a more detailed aspect, the method for establishing a radio linkbetween a mobile terminal and a network in a wireless communicationsystem further comprises deleting all radio bearer information itemsstored for the service during a specific session of the service when thespecific session is terminated. The method may also further comprisedeleting all radio bearer information items stored for the serviceduring a specific session of the service when the mobile terminaldeactivates the service. Also, the method may further comprise driving atimer when storing the radio bearer information and deleting the storedradio bearer information when the timer terminates.

It is to be understood that both the foregoing general description andthe following detailed description of the present invention areexemplary and explanatory and are intended to provide furtherexplanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention andtogether with the description serve to explain the principles of theinvention. Features, elements, and aspects of the invention that arereferenced by the same numerals in different figures represent the same,equivalent, or similar features, elements, or aspects in accordance withone or more embodiments.

FIG. 1 illustrates a block diagram of a related art UMTS networkstructure.

FIG. 2 illustrates a block diagram of the architecture of a related artinterface protocol based 3GPP radio access network specifications.

FIG. 3 illustrates a related art operation for establishing apoint-to-multipoint RB for a specific point-to-multipoint service whilea mobile terminal travels through a plurality of cells.

FIG. 4 illustrates an operation for establishing a point-to-multipointRB for a specific point-to-multipoint service while a mobile terminal istravels through a plurality of cells in accordance with one embodimentof the invention.

FIG. 5 illustrates a flow chart for establishing a point-to-multipointRB when a mobile terminal is moved to a cell wherein point-to-multipointRB information is not updatable during one session of a specificpoint-to-multipoint service in accordance with one embodiment of theinvention.

FIG. 6 illustrates a flow chart for establishing a point-to-multipointRB when a mobile terminal is moved to a cell wherein point-to-multipointRB information is updatable during one session of a specificpoint-to-multipoint service in accordance with one embodiment of thepresent invention.

FIG. 7 illustrates a flow diagram for storing point-to-multipoint RBinformation of a mobile terminal in accordance with one embodiment ofthe present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention relates to a method for establishing a radiobearer between a mobile terminal and a network in a wirelesscommunication system. Referring to FIG. 4, a mobile terminal is movedfrom a cell A to a cell B, from the cell B to a cell C, and from thecell C back to the cell A. During the move, the mobile terminalsequentially performs step 1 in the cell A, step 2 in the cell B, step 3in the cell C and step 4 when returning back to the cell A. Each cell ofFIG. 4 provides a specific MBMS service desired to be received by themobile terminal. The cells transmit the MBMS service to the mobileterminal using a point-to-multipoint radio bearer (RB).

In step 1, the mobile terminal is positioned in the cell A. At thistime, a session of the specific MBMS service, which the mobile terminaldesires to receive, is started. As the session starts, the mobileterminal receives an MBMS RB information message transmitted from thecell A and obtains point-to-multipoint MBMS RB information. The mobileterminal then establishes a point-to-multipoint MBMS RB using theobtained point-to-multipoint MBMS RB information and receives thespecific MBMS service. In addition, the mobile terminal stores theobtained point-to-multipoint MBMS RB information. Thereafter, the mobileterminal is moved from the cell A to the cell B and performs step 2.

In step 2, the mobile terminal positioned in the cell B receives an MBMSRB information message transmitted from the cell B and obtainspoint-to-multipoint MBMS RB information. The mobile terminal thenestablishes a point-to-multipoint MBMS RB using the obtainedpoint-to-multipoint MBMS RB information from the cell B and receives thespecific MBMS service. In addition, the mobile terminal stores theobtained point-to-multipoint MBMS RB information. Thereafter, the mobileterminal is moved from the cell B to the cell C and performs step 3.

In step 3, the mobile terminal positioned in the cell C receives an MBMSRB information message transmitted from the cell C and obtainspoint-to-multipoint MBMS RB information. The mobile terminal thenestablishes a point-to-multipoint MBMS RB using the obtainedpoint-to-multipoint MBMS RB information from the cell C and receives thespecific MBMS service. In addition, the mobile terminal stores theobtained point-to-multipoint MBMS RB information. Thereafter, the mobileterminal is moved from the cell C back to the cell A and performs step4.

In step 4, the mobile terminal has returned to the cell A. Here, themobile terminal does not need to receive the point-to-multipoint MBMS RBinformation message from the cell A again to establish apoint-to-multipoint MBMS RB. Instead, the mobile terminal establishes apoint-to-multipoint MBMS RB using the point-to-multipoint MBMS RBinformation stored in step 1. Once the RB is established, the mobileterminal receives the specific MBMS service.

Referring to FIG. 5, a method is illustrated for establishing an MBMS RBwhen a mobile terminal is moved to a cell wherein MBMS RB information isnot updatable during one session of a specific MBMS service. First, themobile terminal desiring to receive a specific MBMS service is moved toan arbitrary cell providing the specific MBMS service. There, the mobileterminal receives a cell ID transmitted from the cell (step S10). Themobile terminal then receives an MBMS information message through anMBMS Control Channel (MCCH) of the current cell and checks what type ofMBMS RB the current cell establishes for the specific MBMS service (stepS12).

If the current cell provides the specific MBMS using a point-to-pointMBMS RB, the mobile terminal establishes the point-to-point MBMS RBunder the control of a network and receives MBMS service data using theestablished RB (step S14). If the current cell provides the specificMBMS using a point-to-multipoint MBMS RB, the mobile terminal checkswhether its internal memory has stored a cell ID and point-to-multipointMBMS RB information for the current cell (step S16).

If the memory of the mobile terminal includes the cell ID and thepoint-to-multipoint MBMS RB information for the current cell, the mobileterminal establishes the point-to-multipoint MBMS RB for the MBMSservice according to the stored point-to-multipoint MBMS RB information.The mobile terminal then receives MBMS service data using theestablished point-to-multipoint RB (step S18). However, if the memorydoes not have stored either the cell ID or the point-to-multipoint MBMSRB information for the current cell, the mobile terminal receives thepoint-to-multipoint MBMS RB information transmitted through the MCCHfrom the current cell (step S20).

The mobile terminal then stores the received cell ID and thepoint-to-multipoint MBMS RB information of the current cell in thememory and establishes a point-to-multipoint MBMS RB according to thepoint-to-multipoint MBMS RB information of the current cell. After, themobile terminal receives the MBMS service data using the RB (step S22).

Referring to FIG. 6, a method is illustrated for establishing an MBMS RBwhen a mobile terminal is moved to a cell wherein MBMS RB information isupdatable during one session of a specific MBMS service. First, a UTRANtransmits update point-to-multipoint MBMS RB information to the mobileterminal through an MBMS Control Channel (MCCH). This informs theterminal of changes to the point-to-multipoint MBMS RB information ofthe cell the mobile terminal is currently in. The UTRAN manages theupdate information for each cell and each specific MBMS service. Whenthe mobile terminal receives point-to-multipoint MBMS RB informationfrom the cell, it must also receive the update information of thepoint-to-multipoint MBMS RB. While in the cell the mobile terminal hasentered, the mobile terminal stores in a memory the point-to-multipointMBMS RB information, the update information of the point-to-multipointMBMS RB and the cell IDs of the cells which the terminal has enteredthat provide the specific MBMS service using the point-to-multipointMBMS RB.

As shown in FIG. 6, the mobile terminal desiring to receive a specificMBMS service is moved to an arbitrary cell. There, the mobile terminalreceives a cell ID transmitted from the cell providing the MBMS serviceusing a point-to-multipoint MBMS RB (step S30). The mobile terminal thenreceives an MBMS RB information message transmitted through an MBMSControl Channel (MCCH) from the current cell. From the received MBMSinformation message, the mobile terminal obtains update information ofthe point-to-multipoint MBMS RB for the specific MBMS service from (stepS32).

The mobile terminal checks whether the cell ID and point-to-multipointMBMS RB information of the current cell have been previously stored inthe internal memory for the MBMS service (step S34). If the cell ID andthe point-to-multipoint MBMS RB information of the current cell havebeen stored in the memory, the mobile terminal receivespoint-to-multipoint MBMS RB information currently transmitted from thecurrent cell. If, however, either the cell ID or the point-to-multipointMBMS RB information of the current cell has not been stored in thememory, the mobile terminal compares received update information of thepoint-to-multipoint MBMS RB with stored update information of thepoint-to-multipoint MBMS RB. If the received update information isdifferent from the stored update information, the mobile terminalreceives the point-to-multipoint MBMS RB information currentlytransmitted from the current cell (step S38).

Meanwhile, if the cell ID and the point-to-multipoint MBMS RBinformation of the current cell have been stored in the memory, themobile terminal receives the currently transmitted update information.If the currently transmitted update information is the same as thestored update information in the memory, the mobile terminal establishesthe point-to-multipoint MBMS RB for the MBMS service using the storedpoint-to-multipoint MBMS RB information. The mobile terminal thenreceives MBMS service data using the established RB (step S36).

The mobile terminal stores the received cell ID, the point-to-multipointMBMS RB information and the update information of thepoint-to-multipoint MBMS RB of the current cell in the memory. Themobile terminal also establishes the point-to-multipoint MBMS RBaccording to the point-to-multipoint MBMS RB information of the currentcell and then receives the MBMS service data using the RB (step S40).

As described above, the mobile terminal compares update information ofthe point-to-multipoint MBMS RB obtained from the current cell withupdate information of the point-to-multipoint MBMS RB of the currentcell stored in the memory. If the two are different, the mobile terminaldetermines that the content of the currently transmittedpoint-to-multipoint MBMS RB information is different from the content ofthe point-to-multipoint MBMS RB information stored in the memory. If,however, the two are the same, the mobile terminal determines that thecontent of the currently transmitted point-to-multipoint MBMS RBinformation is the same as the content of the point-to-multipoint MBMSRB information stored in the memory. For the update information of thepoint-to-multipoint MBMS RB, an update parameter having an integer valuecan be used.

Referring to FIG. 7, a method is illustrated for storingpoint-to-multipoint MBMS RB information of a mobile terminal. Ifpoint-to-multipoint MBMS RB information of the current cell is receivedas shown in FIGS. 5 and 6, the mobile terminal needs to determinewhether there is space for storing the point-to-multipoint MBMS RBinformation of the current cell in the memory before performing astoring operation.

For this purpose, the mobile terminal manages a threshold value in themobile terminal such as a ‘point-to-multipoint_MBMS_RBinformation_maximum storage number’. When the mobile terminal is tostore a point-to-multipoint MBMS RB information item of the current cellin the memory, the terminal determines if the number ofpoint-to-multipoint MBMS RB information items to be stored exceeds thethreshold value in the mobile terminal. If so, the mobile terminaldeletes one previously-stored point-to-multipoint MBMS RB informationitem in the memory in order to store a currently-receivedpoint-to-multipoint MBMS RB information item of the current cell. If,however, the number of point-to-multipoint MBMS RB information items tobe stored is smaller than the threshold value in the mobile terminal,the mobile terminal stores the point-to-multipoint MBMS RB informationitem of the current cell without removing any previously storedpoint-to-multipoint MBMS RB information items.

The threshold value in the mobile terminal may be determined by theUTRAN and is transmitted from the UTRAN to the terminal before theterminal stores the point-to-multipoint MBMS RB information of thecurrent cell in the memory. The terminal according to its capability mayalso determine the threshold value in the mobile terminal. One thresholdvalue in the mobile terminal is determined for each MBMS service or eachterminal.

Referring to FIG. 7, the maximum number of point-to-multipoint MBMS RBinformation items that the memory can store, namely, the“point-to-multipoint_MBMS_RB_maximum storage number” is three. Thus, thememory of the mobile terminal can store point-to-multipoint MBMS RBinformation for a maximum three cells.

As shown in FIG. 7, among a number of cells such as the cells A, B, C,D, E, F and G which the mobile terminal has passed through, the memoryof the mobile terminal includes the point-to-multipoint MBMS RBinformation received from the cells A, B and D that have established thepoint-to-multipoint MBMS RB for the specific MBMS. Given that themaximum number of point-to-multipoint MBMS information items the memorycan store is three, when the mobile terminal is moved into the cell F,the mobile terminal should remove one of the three point-to-multipointMBMS RB information items stored in the memory in order to be able tostore the point-to-multipoint MBMS RB information of the cell F.Preferably, the mobile terminal removes the point-to-multipoint MBMS RBinformation of a cell positioned farthest from the cell which theterminal is currently in or removes the oldest point-to-multipoint MBMSRB information item among the stored point-to-multipoint MBMS RBinformation items. Accordingly, the mobile terminal removes thepoint-to-multipoint MBMS RB information for the cell A, as shown in FIG.7, and stores the point-to-multipoint MBMS RB information for the cell Fin the memory.

When the mobile terminal stores the point-to-multipoint MBMS RBinformation for one cell, it also stores along with it a cell ID of thecell in the memory. Here, the point-to-multipoint MBMS RB informationand the cell ID are in a one-to-one relationship. Thus, when thepoint-to-multipoint MBMS RB information is stored in the memory, thecell ID for the point-to-multipoint MBMS RB information should be alsostored. Additionally, if the point-to-multipoint MBMS RB information isdeleted from the memory, the cell ID for the point-to-multipoint MBMS RBinformation should also be deleted.

If the update information of the point-to-multipoint MBMS RB, as shownin FIG. 6, is used, the mobile terminal also stores the updateinformation of the point-to-multipoint MBMS RB when storing thepoint-to-multipoint MBMS RB information for one cell. In this case, thepoint-to-multipoint MBMS RB information and the update information ofthe point-to-multipoint MBMS RB are also in a one-to-one relationship.

The mobile terminal can recognize for which cell the storedpoint-to-multipoint MBMS RB information is by checking the storedpoint-to-multipoint MBMS RB information and the cell ID. In addition,the mobile terminal can check for identity between two cell IDs bycomparing a received cell ID for the current cell to a cell ID stored inthe memory. If the received cell ID is the same as the cell ID stored inthe memory, and if point-to-multipoint MBMS RB information having aone-to-one relationship with the stored cell ID has been also stored inthe memory, then the mobile terminal determines that thepoint-to-multipoint MBMS RB information has been stored in the memory.

Furthermore, there are preferably three memory data deletion methods ofthe present invention. In the first memory data deletion method, if thespecific session of the MBMS service is terminated, the mobile terminaldeletes all the point-to-multipoint MBMS RB information items that havebeen stored in the memory for the specific MBMS service during thesession. Thus, the mobile terminal can use the point-to-multipoint MBMSRB information stored in the memory for the specific MBMS service onlyduring one specific session of the MBMS service. Preferably, if themobile terminal receives an RB release message or a session stop messagefor the MBMS service from a system, the mobile terminal deletes thestored point-to-multipoint MBMS RB information for the service from thememory.

In the second memory data deletion method, when the mobile terminaldeactivates the MBMS service, it deletes all the storedpoint-to-multipoint MBMS RB information for the service during thesession from the memory. Thus, the terminal can use thepoint-to-multipoint MBMS RB information stored in the memory for thespecific MBMS service during every session of the service. Preferably,when the mobile terminal deletes UE Context information for the MBMSservice, it deletes all the stored point-to-multipoint MBMS RBinformation for the service from the memory.

In the third memory data deletion method, the mobile terminal drives atimer for all information (cell ID, point-to-multipoint MBMS RBinformation and update information of the point-to-multipoint MBMS RB)in the memory with respect to one cell. The mobile terminal deletes theinformation with respect to the cell when the timer expires.Accordingly, when the terminal stores in the memory thepoint-to-multipoint MBMS RB information with respect to one cell, thetimer for the deletion of the information of the cell is driven.

In the embodiment of FIG. 7, the mobile terminal drives a timer Tf whenstoring the point-to-multipoint MBMS RB information of the cell F. Whenthe timer Tf is terminated, the mobile terminal deletes thepoint-to-multipoint MBMS RB information of the cell F from the memory.When the point-to-multipoint MBMS RB information of the cell F isdeleted, the cell ID and the update information of thepoint-to-multipoint MBMS RB having the one-to-one relationship with theinformation are also deleted. For example, if the mobile terminal storesthe point-to-multipoint MBMS RB information of the cells A, B and D, themobile terminal drives timers Ta, Tb and Tc, respectively. When one ofthe timers is terminated, the mobile terminal deletes the informationcorresponding to the timer from the memory. The mobile terminal uses avalue stored in the mobile terminal or a value received from the systemas the termination time of the timer.

As described above, in the method for establishing an RB in accordancewith the present invention, the mobile terminal stores RB information ofcells that it has passed through, so that when the mobile terminal movesback to a cell previously entered, it establishes an RB using thepreviously stored RB information, rather than re-receiving an MBMS RBinformation message in the corresponding cell. Thus, the mobile terminaldoes not need to re-receive the MBMS RB information messageunnecessarily. Also, data loss as a result of moving between cells isminimized.

Although the present invention is described in the context of mobilecommunication, the present invention may also be used in any wirelesscommunication systems using mobile devices, such as PDAs and laptopcomputers equipped with wireless communication capabilities. Moreover,the use of certain terms to describe the present invention should notlimit the scope of the present invention to certain type of wirelesscommunication system, such as UMTS. The present invention is alsoapplicable to other wireless communication systems using different airinterfaces and/or physical layers, for example, TDMA, CDMA, FDMA, WCDMA,etc.

The preferred embodiments may be implemented as a method, apparatus orarticle of manufacture using standard programming and/or engineeringtechniques to produce software, firmware, hardware, or any combinationthereof. The term “article of manufacture” as used herein refers to codeor logic implemented in hardware logic (e.g., an integrated circuitchip, Field Programmable Gate Array (FPGA), Application SpecificIntegrated Circuit (ASIC), etc.) or a computer readable medium (e.g.,magnetic storage medium (e.g., hard disk drives, floppy disks, tape,etc.), optical storage (CD-ROMs, optical disks, etc.), volatile andnon-volatile memory devices (e.g., EEPROMs, ROMs, PROMs, RAMs, DRAMs,SRAMs, firmware, programmable logic, etc.).

Code in the computer readable medium is accessed and executed by aprocessor. The code in which preferred embodiments are implemented mayfurther be accessible through a transmission media or from a file serverover a network. In such cases, the article of manufacture in which thecode is implemented may comprise a transmission media, such as a networktransmission line, wireless transmission media, signals propagatingthrough space, radio waves, infrared signals, etc. Of course, thoseskilled in the art will recognize that many modifications may be made tothis configuration without departing from the scope of the presentinvention, and that the article of manufacture may comprise anyinformation bearing medium known in the art.

The logic implementation shown in the figures described specificoperations as occurring in a particular order. In alternativeimplementations, certain of the logic operations may be performed in adifferent order, modified or removed and still implement preferredembodiments of the present invention. Moreover, steps may be added tothe above described logic and still conform to implementations of theinvention.

The foregoing embodiments and advantages are merely exemplary and arenot to be construed as limiting the present invention. The presentteaching can be readily applied to other types of apparatuses. Thedescription of the present invention is intended to be illustrative, andnot to limit the scope of the claims. Many alternatives, modifications,and variations will be apparent to those skilled in the art. In theclaims, means-plus-function clauses are intended to cover the structuredescribed herein as performing the recited function and not onlystructural equivalents but also equivalent structures.

1. A method for establishing a radio link between a mobile terminal anda network in a wireless communication system, the method comprising:establishing communication with the network in a cell; receiving andstoring radio bearer information associated with the cell; disconnectingcommunication with the network in the cell; reestablishing communicationwith the network in the cell; and establishing a point-to-multipointradio bearer for a service using the stored radio bearer informationupon reestablishing communication with the network in the cell.
 2. Themethod of claim 1, wherein the radio bearer information is receivedthrough an MBMS control channel (MCCH) of the cell.
 3. The method ofclaim 1, further comprising establishing a point-to-multipoint radiobearer for the service using the radio bearer information and receivingthe service prior to disconnecting communication with the network. 4.The method of claim 1, wherein the service comprises apoint-to-multipoint service.
 5. The method of claim 1, wherein the radiobearer information is point-to-multipoint radio bearer information. 6.The method of claim 1, further comprising receiving a cell ID of thecell.
 7. The method of claim 6, further comprising determining a type ofthe received radio bearer information associated with the cell.
 8. Themethod of claim 7, further comprising: establishing a point-to-pointradio bearer for the service using the received radio bearer informationif the received radio information is determined to be point-to-pointradio bearer information; and receiving the service using thepoint-to-point radio bearer.
 9. The method of claim 6, furthercomprising determining whether the cell ID and point-to-multipoint radiobearer information of the cell are stored in a memory if the receivedradio bearer information is determined to be point-to-multipoint radiobearer information.
 10. The method of claim 9, further comprising:establishing a point-to-multipoint radio bearer for the service usingthe point-to-multipoint radio bearer information if it is determinedthat the cell ID and the point-to-multipoint radio bearer information ofthe cell are stored in the memory; and receiving the service using thepoint-to-multipoint radio bearer.
 11. The method of claim 9, furthercomprising: storing the cell ID and the received radio bearerinformation in the memory if it is determined that either the cell ID orthe point-to-multipoint radio bearer information is not stored in thememory; establishing a point-to-multipoint radio bearer for the serviceusing the received radio bearer information; and receiving the serviceusing the point-to-multipoint radio bearer.
 12. The method of claim 6,further comprising: receiving update information for a service; anddetermining whether the cell ID and point-to-multipoint radio bearerinformation of the cell are stored in a memory.
 13. The method of claim12, wherein the update information is received through an MBMS controlchannel (MCCH) of the cell.
 14. The method of claim 12, furthercomprising: receiving current update information of thepoint-to-multipoint radio bearer associated with the cell if it isdetermined that the cell ID and the point-to-multipoint radio bearerinformation are stored in the memory; comparing the current updateinformation of the point-to-multipoint radio bearer with stored updateinformation of the point-to-multipoint radio bearer; establishing thepoint-to-multipoint radio bearer for the service using the storedpoint-to-multipoint radio bearer information if the current updateinformation of the point-to-multipoint radio bearer is the same as thestored update information of the point-to-multipoint radio bearer; andreceiving the service using the point-to-multipoint radio bearer. 15.The method of claim 12, further comprising: comparing the receivedupdate information with previously stored update information if it isdetermined that either the cell ID or the point-to-multipoint radiobearer information is not previously stored in the memory; and receivingcurrent point-to-multipoint radio bearer information associated with thecell if the received update information is different from the storedupdate information.
 16. The method of claim 15, further comprising:storing the cell ID, the current point-to-multipoint radio bearerinformation and the received update information in the memory;establishing a point-to-multipoint radio bearer for the service usingthe current point-to-multipoint radio bearer information; and receivingthe service using the point-to-multipoint radio bearer.
 17. The methodof claim 1, wherein storing radio bearer information associated with thecell comprises: determining whether a number of radio bearer informationitems to be stored exceeds a threshold value in the mobile terminalparameter; deleting a previously-stored radio bearer information itemand storing the radio bearer information if the number of radio bearerinformation items to be stored exceeds the threshold value of the mobileterminal; and storing the radio bearer information if the number ofradio bearer information items to be stored does not exceed thethreshold value of the mobile terminal.
 18. The method of claim 17,wherein the threshold value of the mobile terminal is determined by thenetwork.
 19. The method of claim 17, wherein the threshold value of themobile terminal parameter is determined by the mobile terminal.
 20. Themethod of claim 17, wherein deleting a previously-stored radio bearerinformation item comprises deleting the radio bearer information item ofa cell positioned farthest from the cell the mobile terminal iscurrently in.
 21. The method of claim 17, wherein deleting apreviously-stored radio bearer information item comprises deleting theoldest radio bearer information item among the stored radio bearerinformation items.
 22. The method of claim 1, further comprisingdeleting all radio bearer information items stored for the serviceduring a specific session of the service when the specific session isterminated.
 23. The method of claim 1, further comprising deleting allradio bearer information items stored for the service during a specificsession of the service when the mobile terminal deactivates the service.24. The method of claim 1, further comprising: driving a timer whenstoring the radio bearer information; and deleting the stored radiobearer information when the timer terminates.
 25. An apparatus forestablishing a radio link between a mobile terminal and a network in awireless communication system, the apparatus comprising: means forestablishing communication with the network in a cell; means forreceiving and storing radio bearer information associated with the cell;means for disconnecting communication with the network in the cell;means for reestablishing communication with the network in the cell; andmeans for establishing a point-to-multipoint radio bearer for a serviceusing the stored radio bearer information upon reestablishingcommunication with the network in the cell.
 26. The apparatus of claim25, wherein the radio bearer information is received through an MBMScontrol channel (MCCH) of the cell.
 27. The apparatus of claim 25,further comprising means for establishing a point-to-multipoint radiobearer for the service using the radio bearer information and receivingthe service prior to disconnecting communication with the network. 28.The apparatus of claim 25, wherein the service comprises apoint-to-multipoint service.
 29. The apparatus of claim 25, wherein theradio bearer information is point-to-multipoint radio bearerinformation.
 30. The apparatus of claim 25, further comprising means forreceiving a cell ID of the cell.
 31. The apparatus of claim 30, furthercomprising means for determining a type of the received radio bearerinformation associated with the cell.
 32. The apparatus of claim 31,further comprising: means for establishing a point-to-point radio bearerfor the service using the received radio bearer information if thereceived radio information is determined to be point-to-point radiobearer information; and means for receiving the service using thepoint-to-point radio bearer.
 33. The apparatus of claim 30, furthercomprising means for determining whether the cell ID and thepoint-to-multipoint radio bearer information of the cell are stored in amemory if the received radio bearer information is determined to bepoint-to-multipoint radio bearer information.
 34. The apparatus of claim33, further comprising: means for establishing a point-to-multipointradio bearer for the service using the point-to-multipoint radio bearerinformation if it is determined that the cell ID and thepoint-to-multipoint radio bearer information of the cell are stored inthe memory; and means for receiving the service using thepoint-to-multipoint radio bearer.
 35. The apparatus of claim 33, furthercomprising: means for storing the cell ID and the received radio bearerinformation in the memory if it is determined that either the cell ID orthe point-to-multipoint radio bearer information is not stored in thememory; means for establishing a point-to-multipoint radio bearer forthe service using the received radio bearer information; and means forreceiving the service using the point-to-multipoint radio bearer. 36.The apparatus of claim 30, further comprising: means for receivingupdate information for a service; and means for determining whether thecell ID and point-to-multipoint radio bearer information of the cell arestored in a memory.
 37. The apparatus of claim 36, wherein the updateinformation is received through an MBMS control channel (MCCH) of thecell.
 38. The apparatus of claim 36, further comprising: means forreceiving current information of the point-to-multipoint radio bearerassociated with the cell if it is determined that the cell ID and thepoint-to-multipoint radio bearer information are stored in the memory;means for comparing the current update information of thepoint-to-multipoint radio bearer with stored update information of thepoint-to-multipoint radio bearer; means for establishing apoint-to-multipoint radio bearer for the service using the storedpoint-to-multipoint radio bearer information if the current updateinformation of the point-to-multipoint radio bearer is the same as thestored update information of the point-to-multipoint radio bearer; andmeans for receiving the service using the point-to-multipoint radiobearer.
 39. The apparatus of claim 36, further comprising: means forcomparing the received update information with previously stored updateinformation if it is determined that either the cell ID or thepoint-to-multipoint radio bearer information is not previously stored inthe memory; and means for receiving current point-to-multipoint radiobearer information associated with the cell if the received updateinformation is different from the stored update information.
 40. Theapparatus of claim 39, further comprising: means for storing the cellID, the current point-to-multipoint radio bearer information and thereceived update information in the memory; means for establishing apoint-to-multipoint radio bearer for the service using the currentpoint-to-multipoint radio bearer information; and means for receivingthe service using the point-to-multipoint radio bearer.
 41. Theapparatus of claim 25, wherein storing radio bearer informationassociated with the cell comprises: means for determining whether anumber of radio bearer information items to be stored exceeds athreshold value of the mobile terminal; means for deleting apreviously-stored radio bearer information item and storing the radiobearer information if the number of radio bearer information items to bestored exceeds the threshold value of the mobile terminal; and means forstoring the radio bearer information if the number of radio bearerinformation items to be stored does not exceed the threshold value ofthe mobile terminal.
 42. The apparatus of claim 41, wherein thethreshold value of the mobile terminal is determined by the network. 43.The apparatus of claim 41, wherein the threshold value of the mobileterminal is determined by the mobile terminal.
 44. The apparatus ofclaim 41, wherein the means for deleting a previously-stored radiobearer information item deletes the radio bearer information item of acell positioned farthest from the cell the mobile terminal is currentlyin.
 45. The apparatus of claim 41, wherein the means for deleting apreviously-stored radio bearer information item deletes the oldest radiobearer information item among the stored radio bearer information items.46. The apparatus of claim 25, further comprising means for deleting allradio bearer information items stored for the service during a specificsession of the service when the specific session is terminated.
 47. Theapparatus of claim 25, further comprising means for deleting all radiobearer information items stored for the service during a specificsession of the service when the mobile terminal deactivates the service.48. The apparatus of claim 25, further comprising: means for driving atimer when storing the radio bearer information; and means for deletingthe stored radio bearer information when the timer terminates.